Method for injecting viscous fluid into the eye to life retinal membrane

ABSTRACT

A method for injecting viscous material into the eye. In the injection into the eye, sufficient material is injected to separate a membrane from the retina so that intraocular scissors may be manipulated between the membrane and the retina to cut the attachment points. The membrane is then aspirated away. The injection is done using a standard glue injector with a one-shot and a continuous mode. The glue injector is pneumatically coupled through a sterile filter and a custom adaptor to a sterile syringe storing the material to be injected.

This application is a continuation of application Ser. No. 07/209,503,filed June 21, 1988, now abandoned.

BACKGROUND OF THE INVENTION

The invention pertains to the field of intraocular surgery, and, moreparticularly, to surgical procedures for removal of pre-retinal orpost-retinal membranes.

It is a frequent post-operative complication following surgicalprocedures in the posterior region of the eye that a glia cell membranewill form and attach itself to the retina. Anytime the choroid layer isstimulated such as by cutting, laser burning, lesion caused by probingor cryo or thermal damage, or any other form of stimulation, fibro andglia cells will be pumped from the choroid by pneumatic processes. Gliacells are glue-like and serve to repair damage surrounding the lesionformed by the stimulation. This excretion of glia cells is often used to"glue" a detached retina to the choroid. Unfortunately, the body'scontrol mechanisms of secretion of fibro and glia cells are not finelytuned enough to stop secretion of the cells at the precise time whenenough cells have been excreted to do the job. Excretion of excess cellsoften results in formation of a membrane of cells over the retinabetween the retina and the lens of the eye resulting in obstruction ofthe light path to the retina. Sometimes, in the case of detachedretinas, the membrane forms between the retina and the choroid.

The formation of these membranes is called proliferative disease. Thisdisease frequently is a post-operative complication of surgicalprocedures for reattachment of detached retinas. One of the negativeeffects that results from this phenomenon is that the glia cellsinitially form a single cell layer membrane over the retina or betweenthe retina and the choroid. This membrane is attached to the retina atvarious points by what are sometimes referred to as "nails". The retinais normally attached to the choroid by a structure which is similar toVELCRO™ brand hook and loop fabric.

There is a problem of spontaneous detachment of the retina ifproliferative disease develops. This can occur for the following reason.The membranes initially form as a single cell layer. Later, the cellsoften rearrange themselves into a multiple cell layer without growingfurther. Attachments to the retina at the locations of the "nails" maybe quite strong. Because the same number of cells that were formerly asingle cell layer have become a multiple cell thickness layer, themembrane tends to shrink. This shrinkage causes stresses on the retinaat the positions of the "nails" which can result in holes being pulledin the retina or in spontaneous detachment of the retina from thechoroid.

Another problem of membrane formation is that in the prior art processfor removing such membranes, forces can be applied to the retina by thetools used or through the "nail" connection points to damage the retinastructure. Typically, this happens by pulling a hole in the retina atthe position of a nail or by punching a hole in the retina throughmistakes in manipulation of the tools used. Also, the process ofremoving a post-retinal membrane, i.e., one between the retina and thechoroid, can result in cutting off circulation of blood to the rods andcones of the retina. To understand these problems further, consider thefollowing.

In the prior art, surgeons have removed these membranes from the retinausing several techniques. One such technique is to take a verticalintraocular scissors with the blades closed and insert the tip of thescissors between the membrane and the retina. This is a very delicateprocess and requires great manual dexterity since the space between themembrane and the retina is not large. After the scissors are inserted,the blades are very gently opened to separate the membrane from theretina. This process is continued until the location of a "nail" isencountered. Then a horizontal intraocular scissor is inserted in thespace between the cell membrane and the retina in such a manner as tocut the "nail". This process is repeated until the "nails" have beenfound and severed or pulled loose. After the cell membrane has beenseparated in this manner from the retina, it is usually removed using avitrectomy probe.

Another prior art technique is to use an instrument which has afiber-optic probe with a hook. The hook is very small and is formed ofthe tip of the light pipe. The hook is used by inserting its tip betweenthe membrane and the retina and separating the membrane from the retinaby pulling gently on the membrane.

The difficulty with both of these prior art approaches is that damage tothe retina can easily result. One type of damage can result if themechanical forces applied to the membrane and transmitted to the retinaat the locations of the "nail" are too large. This can result in holesbeing pulled in the retina at the position of the "nails". Further,detachment of the retina from the choroid can also result if the forceexerted on the retina through the nails exceeds the force holding theretina to the choroid. Another type of damage that can result is throughinadvertent movement of the instrument while the retina is engaged onthe hook which results in excessive force being applied to the retina.If the tools are not manipulated with great skill, holes can be poked inthe retina. These holes result from the relatively concentrated forcesacting on the retina at the tips of the instruments. Even a slightmisapplication of force can result in this type of damage to the retina.

Accordingly, a need has arisen for a system which can be used to gentlyseparate the membranes from the retina without causing spontaneousdetachment of the retina and without pulling or punching holes in theretina thereby allowing the "nails" to be cut without damage to theretina.

SUMMARY OF THE INVENTION

According to the teachings of the invention, an apparatus and method istaught for injecting a viscous fluid in the space between the membraneand the retina. This viscous fluid forms pockets in the space betweenthe membrane and the retina all around the "nail" attachments. Thesepockets of viscous fluid apply diffuse pressure to the membrane andretina to separate these structures. Separation of the membrane from theretina allows horizontally oriented intraocular scissors to be workedinto the space between the membrane and the retina through the viscousfluid. These scissors may be worked to the position of the "nails" whichmay then be cut thereby separating the membrane from the retina.Sometimes the process of injecting the viscous material alone will pullthe nails loose. This process may be done without endangering the retinabecause the pressure applied to the retina is very diffuse and is notlocalized in one small area thereby creating stresses in that area whichexceed the strength of the retina.

In the preferred embodiment, a viscous fluid with self-adheringproperties is used for injection. Several brands of fluid have beenfound to be adequate for purposes of practicing the invention. One suchcandidate is HEALON brand sodium hyaluronate marketed by Pharmacia.Another fluid which is acceptable for purposes of practicing theinvention is AMVISC brand sodium hyaluronate marketed by Johnson andJohnson.

The fluid is injected using a modified glue injection device which iscommercially available. In a preferred embodiment, a model 1000×L glueinjector manufactured by EFD of East Providence, R.I. is used. This glueinjector is coupled to a source of pressurized air and has a pressureregulator. The device also generates its own vacuum using a venturi andthe pressurized air. The glue injector also has a foot switch and apressurized air output which is connected to a syringe in which theviscous fluid is stored. The amount of pneumatic pressure at thepressurized air output is controlled by manipulation of a control on thefront panel of the unit which controls the internal pressure regulator.The pressure may be set at anywhere between zero and 40 pounds persquare inch.

The device has two modes. The first mode is the continuous mode, and thesecond mode is the "one shot" mode. In the first mode, when the footswitch is depressed, pressurized air builds up to the pressure set bythe pressure regulator and continues at that level for as long as thefoot switch is pressed. When the foot switch is released, the outputpneumatic tube is either vented to atmosphere or vacuum is applied to itto prevent "woozing" of fluid out of the needle of the syringe connectedto the pneumatic output. The level of vacuum which is applied duringthis stage is controlled by another control on the front panel of theunit. In the second mode, a pressure pulse having a duration which isvariable is applied to the pneumatic output tube. This pulse starts whenthe foot switch is pressed, and ends when the predetermined interval haspassed. The duration of the pulse is set by a timer control which can bemanipulated from the front panel of the unit. The standard glueinjection syringe of the system is replaced by a sterile HEALON brandsodium hyaluronate or other viscous fluid injection syringe onto whichthe pneumatic output tube from the pressure regulation unit isconnected. A special sealing adaptor comprising a threaded bezel ringmated with a threaded adaptor having an O ring is used to form amechanical bond between the syringe and the pneumatic output tube and toform a pneumatic seal. The bezel ring fits around the syringe andengages a flange thereof. A plunger or piston inside the injectionsyringe is in pneumatic communication with the pressure regulation unitthrough the special adaptor just described and the pneumatic hose. Thisallows pneumatic pressure applied by the pressure regulation unit to becoupled to the piston to force it to move downward in the syringe. Thisforces viscous fluid stored in the syringe from the tip of a hollowneedle which is affixed to the cylinder of the syringe. A filter isplaced in the pneumatic line between the pressure regulating unit andthe syringe. This filter filters out all foreign bodies havingdimensions greater than a particular size from the pneumatic air flow tothe syringe.

A method of using the above described apparatus for performing asurgical procedure to remove either a pre or post-retinal membrane is asfollows. The syringe is attached to the pressure regulating unit. Thepressure regulating unit is located outside the sterile field, and theattachment of the sterile syringe is made to the pneumatic tube endafter it has been placed in the sterile field. The desired pneumaticpressure is than set by manipulation of the appropriate front panelcontrol. This is done regardless of whether the continuous or one-shotmode is selected. Next, the one-shot or continuous mode is selected bymanipulation of the appropriate switch on the front panel of thepressure regulation unit. In the one-shot mode, the desired pulseduration is set by manipulating the appropriate control on the frontpanel. Then the vacuum level which will be applied to the pneumaticoutput tube upon completion of the pneumatic pressure pulse is set bymanipulation of the appropriate control on the front panel of thepressure regulation unit. In the continuous mode, both the pressure andvacuum level are set in a similar fashion. Pressure and vacuum levelsfor either mode are set using experimental injections outside the eyeand inside the sterile field so as to obtain the desired injection ratefor the then existing conditions of temperature and health, i.e.,strength, of the retina. The surgeon will have already made anassessment of the strength of the retina from previous surgery.

Next, the tip of the needle is placed in the space between the retinaand the pre or post-retinal membrane. Thereafter, the foot switch isdepressed to cause injection of the HEALON brand sodium hyaluronate intothe space between the pre or post-retinal membrane and the retina. Thiscauses the pre or post-retinal membrane to "inflate" as it is pushedaway from the retina by the injection of the viscous fluid. The surgeonexercises judgement to stop the injection when it looks like too muchstress is being applied to the retina through a nail attachment. Thisinjection process is repeated at a sufficient number of locations toeither break and/or isolate all the "nails" or connection points betweenthe pre or post-retinal membrane and the retina itself. The "nails"which have not been broken by the injection process itself are then cutusing horizontally oriented intraocular scissors.

Once all the connection points have been severed, the membrane isusually removed using a vitrectomy probe or other aspiration device. TheHEALON brand sodium hyaluronate or other viscous material remaining inthe eye is then removed using a vitrectomy probe or other aspirationdevice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an anatomical sketch of the eye illustrating the relationshipbetween the retina and the choroid and showing the manner of injectionof fluid between a pre-retinal membrane and the retina.

FIG. 2 is an illustration showing the structure of the eye and apre-retinal membrane after injection of viscous fluid surrounding a nailattachment point.

FIG. 3 is a diagram of the apparatus of the invention.

FIGS. 4A and 4B are exploded view of the injection syringe and theconnection apparatus for connecting the syringe to the pneumatic hose.

FIG. 5 is a cross-sectional view of a threaded adaptor for use with athreaded bezel ring for attaching the syringe to the pneumatic hose.

FIGS. 6A and 6B are end and cross-sectional views, respectively, of thethreaded bezel ring for use with the threaded adapter of FIG. 5.

FIGS. 7A and 7B are end and cross-sectional views of a bayonet typeconnector for connecting the syringe to the pneumatic hose.

FIG. 8 is a diagram showing the internal structure of the off-the-shelf1000×L glue injector used as one component of a system according to theteachings of the invention.

FIG. 9 is an electrical schematic diagram of the off-the-shelf 1000×Lglue injector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is shown in cross section an anatomicaldiagram of the eye. The particular portions of the eye of interest arethe retina shown at 10 and the choroid shown at 12. Sometimes the retinabecomes detached from the choroid for various reasons. When thishappens, a medical procedure is performed to reattach the retina to thechoroid. This is usually done by causing a lesion in the choroid by anyone of several possible methods. Often laser energy is beamed throughthe sclera shown at 14 and through the choroid 12 to cause the lesion.Cutting, the application of heat or other mechanical stimulation mayalso be used to cause this lesion. The wound in the choroid causesgrowth of glia cells. These glia cells grow out from the lesion in thechoroid and, because of their glue-like properties, they tend toreattach the retina to the choroid. However, because the body does nothave sufficient control over the growth of these glia cells, theyfrequently form a single layer of cells in the form of a membranebetween the retina and the lens 16. A portion of such a pre-retinalmembrane is shown at 18. These pre-retinal membranes have a tendency toattach themselves to the retina at randomly spaced locations. Suchattachment points or "nails" are shown symbolically at 20 and 22.

There are several difficulties that a preretinal membrane causes as apost-operative complication. First, the membrane obstructs light passagethrough the vitreous body to the retina thereby obstructing vision.Second, the pre-retinal membrane tends to rearrange itself from aone-cell layer membrane to a two-cell layer membrane. A segment of sucha rearranged membrane is shown at 24. This latter phenomena causesdifficulty because in the process of rearranging itself, the preretinalmembrane shrinks thereby putting stress on the retina through the "nail"connections. This stress can wrinkle, tear, or detach the retina and isquite undesirable. A solution to this problem is to remove thepreretinal membrane.

As noted above, the postoperative membrane is not always in apre-retinal position. Sometimes it also forms between the retina and thechoroid. Nevertheless, the same considerations apply since thepost-retinal membrane also attaches itself to the retina sporadically atnail connection points and will rearrange itself from a single-celllayer to a multiple-cell layer thereby causing the problems noted above.

It has been found by the applicants that a good way to remove a membraneis to inject a viscous, selfadhering fluid such as HEALON brand gelbetween the membrane and the retina. This is done by inserting a needleinto the interstices between the membrane and the retina and pumping theviscous gel into the interstices. FIG. 1 shows such a needle 26 inposition to begin pumping fluid at 26.

Referring to FIG. 2, there is shown the result of injection of a viscousgel in the interstices between the membrane and the retina 10. Theinjection process forms bubbles of injected gel shown at 28 and 30.These bubbles lift the membrane 24 away from the retina 10 by applyingdiffuse pressure to both the retina and the membrane over a large area.This "large area" is relative to the stresses which are caused on theretina by tools used in the prior art. The prior art method of removinga membrane was using a mechanical hook to engage the membrane and liftit away from the retina. If the hook is not manipulated correctly, thetip of the hook impacts the retina in a small area. This causeslocalized forces which can raise the stress level in the retina abovethe levels that can be easily withstood by this delicate structure. Thediffuse nature of the pressure applied by the injected gel according tothe teachings of the invention tend to distribute the stress widely overthe surface of the retina 10 and the membrane 24. Because the forcesapplied by the injected gel are spread out over a large area, the stresslevel at any particular point of the retina is less than the stressimposed in the retina in the prior art methods. The result of impropermanipulation of the tools used in the prior art methods often was a tornretina or a retina with a hole punched therein. By eliminating the needto contact the retina with any hard instrument, the potential for damageto the retina is substantially reduced using the teachings of theinvention.

Once injection of the gel is completed and the structure is as shown inFIG. 2 throughout the area covered by the membrane, the membrane may bedetached. The membrane cannot simply be pulled off the retina using ahooked instrument since the nail attachments will tend to detach theretina from the choroid or tear a hole in the retina at the point ofattachment. Therefore, it is necessary to cut the nail attachments withhorizontally-oriented intraocular scissors. This is done by working thepoint of the intraocular scissors through the injected gel to theposition of the nail and cutting the nail. This sequence of events isnot depicted in FIG. 2, but those skilled in the art can appreciate howit is done.

Referring to FIG. 3 there is shown a picture of a system which isadapted for injecting the gel 28 to lift the membrane away from theretina. The system is comprised of a pneumatic pressure and vacuumcontrol unit 32 which will hereafter be referred to as the control unit.System unit 32 is an off-the-shelf glue injection controllermanufactured by EFD of East Providence, R.I. Its model designation is1000×L. The control unit 32 is coupled to an air pressure source by aconnector (not shown) on the back side of the unit. In some embodiments,the control unit 32 may be coupled to a source of vacuum by a vacuuminput (not shown) on the back side of the unit. The purpose of thecontrol unit 32 is to regulate the amount of pneumatic pressure appliedto a pneumatic output 34. This pneumatic output is coupled by apneumatic hose 34a through an air filter 36 to a syringe 38. Thissyringe has a piston 40 therein which is driven by the pneumaticpressure toward an injection needle 26 thereby forcing any fluid storedin the cavity 42 of the syringe out from the tip of the injection needle26. There are generally two types of syringes used for the same purpose.They differ in the type of flange that is attached to the syringe body.One type of syringe has two ears extending from opposite sides of thesyringe barrel such as the syringe shown in FIG. 4. Another type ofsyringe has a polygon or round or nearly round shaped flange whichsurrounds the barrel. The two different types of syringe requiredifferent types of adapters for connection to the pneumatic hose.

The air filter 36 serves to filter any microscopic size particles fromthe flow of air in the pneumatic tubing 34. This air filter shouldeither be sterile and disposable or autoclavable. The syringe 38, needle26, and piston 40 also should be either autoclavable or sterile anddisposable.

The control unit has an air pressure gauge 44 for monitoring the levelof pneumatic pressure which is being applied to the syringe 38. Theamount of pressure applied is controlled by an air pressure regulatorinside the control unit which is controlled by a front panel knob 46.The control unit 32 has a power on/off switch 48, and a mode controlswitch 50. This mode control switch switches the control unit between asteady state mode and a "one-shot" mode. In the steady state mode, alevel of pneumatic pressure set by manipulation of the air pressureregulator control knob 46 will be applied to the pneumatic output 34beginning when a foot peddle control 52 is depressed and terminatingwhen the foot peddle control 52 is released. In the "one-shot" mode, apneumatic pulse is applied to the pneumatic output 34. The air pressuremagnitude of this pulse is set by manipulation of the air pressureregulator control knob 46. The duration of this pneumatic pulse iscontrolled by manipulation of a time control knob 54. The pneumaticpulse is issued by the control unit 32 when the foot pedal 52 isdepressed. The pneumatic pulse automatically terminates at the end ofthe interval set by the time control knob 54, regardless of when thefoot pedal 52 is released.

For some low viscosity fluids it is advantageous to apply vacuum to thepneumatic output 34 at the end of the pneumatic pressure cycle. Thisvacuum pulls the piston 40 away from the needle 26, thereby aspiratingfluid back into the needle 26. This prevents a last drop of fluid whichmay be clinging to the tip of the needle 26 from dripping from theneedle tip at an inconvenient time or at some unintended location. Thelevel of vacuum which is applied to the pneumatic output 34 iscontrolled by a vacuum control manipulation knob 56 on the front panelof the control unit. The level of vacuum may be adjusted with the aid ofa vacuum pressure gauge 58. The level of vacuum set by the vacuumcontrol knob 56 will automatically be applied at the end of everypneumatic pulse or application of pneumatic pressure to the output 34.If no vacuum aspiration is desired, the vacuum control knob 56 ismanipulated so that zero vacuum pressure is indicated on the vacuumpressure gauge 58. Vacuum is generated in the control unit 32 by use ofa venturi to convert pneumatic pressure of escaping air tosubatmospheric pressure.

The pneumatic pressure on the output line 34 may be set anywhere from 1to 100 psi. Typical operating pressures are on the order of 30-40 psidepending upon temperature and viscosity.

In operation, the control unit 32 is located outside the sterile field.A sterile pneumatic hose 34 is then unpackaged in this sterile field,and one end is connected to the pneumatic output. A sterile air filter36 is then attached to the other end of the pneumatic hose 34 within thesterile field. A sterile prepackaged syringe containing the gel to beinjected is then coupled to a segment of sterile pneumatic hoseconnected to the output of the air filter 36. In the preferredembodiment, the syringe 38 contains HEALON brand gel in cavity 42. Moredetails on the structure of the syringe 38 and its adapter for couplingto the segment of pneumatic hose 60 will be given below.

Following attachment of the syringe to the pneumatic hose segment 60,the following procedure is used to perform the surgical procedure.First, the desired pneumatic peak pressure is set using the air pressureregulator control knob 46. It is desired to have a very small flow ratefor injection of the gel to avoid applying sudden excess amounts ofpressure to the retina and membrane. Therefore, the maximum pressureshould be set no higher than 30-40 psi. The pressure is adjustedexperimentally for the current conditions of viscosity and operatingroom temperature by placing the system in continuous or one-shot modeand depressing the foot pedal and observing the flow rate of gelemerging from the tip of the injection needle 26. If a higher flow rateis required, the air pressure regulator control knob 46 is manipulatedto increase the pressure. If a lower flow rate is desired, a lowerpneumatic pressure is set using the air pressure regulator control knob46. The desired vacuum level, if any, is also set for the currentconditions of viscosity and temperature.

Next, the appropriate mode is set. If the one-shot mode is selected, thetime duration of the pneumatic pulse is set using time control knob 54.The foregoing steps for setting the desired injection rate are basedupon not only the current conditions of temperature and viscosity, butalso upon the health or strength of the retina. This latter informationis generally available based upon previous surgery which caused thestimulation of the choroid which generated the membrane.

Next, the tip of the needle 26 is placed in the space between the retinaand the membrane. Injection of fluid from the cavity 42 is thenperformed while the surgeon observes the inflation of the membrane.Injection is stopped if it looks like too much stress is being appliedto the retina through a "nail" connection. This injection process isperformed at a sufficient number of locations to thoroughly break offand/or isolate all the nail connection points between the membrane andthe retina. Care is exercised to not pull holes in the retina at thepositions of the nails or detach the retina from the choroid by applyingexcess force to the retina through the nails. The unbroken nails arethen cut using horizontally oriented intraocular scissors. Finally, themembrane is removed through use of a vitrectomy probe or otheraspiration instrument. The injected gel may then be removed with avitrectomy probe or any other aspiration instrument.

Referring to FIGS. 4A and 4B, there is shown an exploded view of theinjection syringe. The syringe is comprised of a main body 38 having aflange 62 and a syringe holder 64. The syringe holder 64 has a lock-inmechanism 66 which engages the flange 62. In the embodiment shown inFIGS. 4A and 4B, the flange 62 is engaged in the lock-in mechanism 66 inbayonet fashion, as shown generally at 68. The syringe body 38 has apiston 40 therein which is shown in phantom in FIG. 4A. This pistonforms an air-tight and liquid-tight seal with the inside walls of thesyringe body 38. The syringe body 38 terminates in an injection needle26 (not shown) which is protected by a cover/handle 70. Thiscover/handle terminates in a projection 72 which can be threaded intothe piston 40 for manual manipulation of the piston.

The syringe depicted in FIG. 4A is, with the exception of the syringeholder 64, a off-the-shelf HEALON storage syringe which is availablefrom the manufacturer of HEALON brand gel. The syringe holder 64 is aspecialized adapter which is constructed to allow the piston 40 to bemanipulated by pneumatic pressure and vacuum in the input line 60. Thus,the cover 70 is only for purposes of protecting the injection needle 26(not shown) and maintaining its sterility.

The syringe holder 64 engages the syringe body 38 to form a mechanicalbond between the syringe body 38 and the pneumatic hose 60, as well as apneumatic seal. To that end, the syringe holder 64 has an internalpassageway 74 which is in fluid communication with the pneumatic tubing60. When the syringe holder 64 engages the syringe body 38, an extension76 of the syringe body on the syringe holder side of the flange 62slides into the passageway 74 when the flange 62 is engaged in thelock-in mechanism 66. An O-ring seal (not shown) inside the passageway74 engages the side walls of the section 76 of the syringe body to formthe pneumatic seal.

More details of the structure of the syringe holder 64 are illustratedin FIG. 5. The syringe holder is comprised of a main body 64 with alock-in mechanism 66 formed thereon, typically by casting or injectionmolding. The main body has an internal passageway 74 which is in fluidcommunication with a second passageway 77 in a pneumatic-tube-engagingprojection 78. This projection 78 has ribs 80 for engaging the flexiblepneumatic tubing to form a mechanically sound connection and a pneumaticseal. The internal cavity 74 has a groove 82 formed therein in which anO-ring is placed. This O-ring should be of silicone or other flexiblebut autoclavable material.

In the embodiment shown in FIG. 5, the outside edges of the lock-inmechanism 66 are threaded. These threads engage similar threads on theinside of a bezel ring 84 shown in FIGS. 6A and 6B. FIGS. 6A and 6B showa bezel ring for engaging the flange 62 in FIG. 4 as an alternativemechanism to the bayonet lock-in mechanism shown in FIG. 4. FIG. 6A is aplan view of this bezel ring, while FIG. 6B is a sectional view of thering taken along the line 6B--6B' in FIG. 6A. The bezel ring iscomprised of a main body 84 having a threaded portion 86 and an aperture88. The aperture 88 slides over the main body 38 of the syringe in FIG.4 until the flange 62 rests against the surface 90 shown in FIG. 6B. Theportion 76 of the syringe main body extends through the aperture 88 inFIG. 6B into the main body 64 of the syringe holder. The inside diameterof the threaded portion 86, shown at A in FIG. 6B, matches the outsidediameter of the lock-in portion 66 of the syringe holder 64. The lock-inportion 66 is then threaded into the threaded portion 86 of the bezelring of FIG. 6B to form the mechanical union between the syringe holder64 and the syringe body 38. The O-ring in the groove 82 then forms apneumatic seal by engaging the walls of the portion 76 of the syringebody. This O-ring is shown at 92 in FIG. 5.

Referring to FIGS. 7A and 7B, there is shown the preferred embodiment ofthe syringe holder 64 with a bayonet-type lock-in mechanism 66. FIG. 7Ashows an end view of the syringe holder looking down the center line,while FIG. 7B shows a section of the syringe holder taken along thesection line 7B--7B' in FIG. 7A. As in the case of the syringe holdershown in FIG. 5, the syringe holder has an internal passageway 92 inwhich is formed a groove 94 in which a flexible, autoclavable O-ring isseated. This O-ring engages the side walls of the portion 76 of thesyringe barrel in FIG. 4 to form a pneumatic seal. Essentially the onlydifference between the syringe holder depicted in FIG. 7A and 7B and thesyringe holder shown in FIGS. 5, 6A, and 6B is the lock-in mechanism.This lock-in mechanism 66 is comprised of an annular projecting portion66 in which are formed a pair of L-shaped grooves 96 and 98, which arebest seen in FIG. 4. These grooves engage the two projecting tips of theflange 62. To operate the lock-in mechanism, the portion 76 of thesyringe barrel is inserted in the passageway 92 and engaged with theO-rings to form the pneumatic seal. This process pulls the projectingportions of the flange 62 into the L-shaped grooves. When the flange 62is flush with the wall 100 in FIG. 7B, the syringe 38 is rotatedapproximately one-eighth of a turn to the right, thereby twisting theflange 62 in the lock-in 66 so as to lock the syringe barrel in place inthe syringe holder lock-in mechanism as shown at 68 in FIG. 4.

Referring to FIG. 8, there is shown the structure of the Model 1000×Lglue injector system unit 32 used in one embodiment of the invention.Pressurized gas from an external source, preferably air, enters systemunit 32 at port 400. In the "one-shot" mode, the following sequence ofevents occurs when the footpedal (not shown in FIG. 8, but shown as 52in FIG. 3) is pressed down. First, upon depression of the footpedal 52,a solid state timer 402 is energized. The timer 402 is EFD part number2-2006-24PR in this embodiment. A set of four DIP switches 404 are setas shown in FIG. 8 (switches 1 and 2 are off and switches 3 and 4 are onpreceeding from left to right). The timer 402 then begins a countdownfrom a preset count. A LED 406 located on top of the system unit 32lights to indicate a cycle is active. This LED remains on until thecycle is complete.

The timer 402 energizes a solenoid which controls the output air channel410. Input pressurized air at approximately 100 psi from input airchannel 412 enters a pressure regulator 414. This device outputsregulated pressurized air into channel 415 and channel 426. Channel 416is coupled to a pressure gauge 418 which provides an indication of theoutput pressure of the regulator 414 to the user. The output pressure ofthe pressure regulator 414 is controlled by the user by adjusting a knob420 on the front panel. The pressure regulator is EFD part number2-2002-XL.

When the solenoid 408 is energized, vacuum (generated by a vacuumtransducer described below) is decoupled from output channel 410. At thesame time, the pressurized gas in channel 415 is coupled to the outputchannel 410. In this embodiment, the solenoid 408 is EFD part number2-2003-24N. The regulated pressure output gas in channel 410 flows outto the syringe (not shown in FIG. 8, but reference numeral 38 in FIG. 3)via pneumatic output 34 and sterile surgical tubing 34a (shown in FIG.3). Referring to FIG. 3, this gas pressure pushes the sterile viscousmaterial stored in the syringe out the tip of the needle 24.

Referring again to FIG. 8, at the end of the preset time, the timer 402shuts off thereby denergizing the solenoid 408. The pressurized gas inthe syringe, surgical tubing and the output channel 410 is thenexhausted to the atmosphere at exhaust port 422. The duration of thepressurized gas pulse can be varied by manipulation of the front paneltimer control 54 in FIG. 8. Simultaneously, the solenoid 408 couplesvacuum generated by a vacuum transducer 434 to the output channel 410.Referring again to FIG. 3, this vacuum draws the piston 40 of thesyringe 48 in FIG. 3 back toward the pneumatic outlet thereby suckingany remaining viscous material at the tip of the needle that is notsupposed to be injected back into the syringe.

Vacuum is created by bleeding pressurized gas from channel 430 through aneedle valve 432 and the vacuum transducer 434. The needle valve is EFDpart number 2-2176-XL. The vacuum transducer 434 is EFD part number2-2170LV. The vacuum transducer converts pressurized gas to vacuum inchannel 436 which the solenoid 408 couples to output channel 410 atcertain times as described above. The pressurized gas channel 430 iscoupled by a tee connection 440 to the input pressurized gas channel412. The needle valve 432 controls the volume flow rate of pressurizedgas in a channel 442 to the vacuum transducer 434. A channel 444,coupled by a gauge restrictor 446 to the needle valve, couples the gaspressure in channel 442 to a pressure gauge 450 which provides anindirect indication on the front panel of the system unit 32 of therelative level of vacuum being generated by the vacuum transducer 434.

This completes a "one-shot" pulsed type operation.

Steady state or continuous injection is also possible by switching thesteady switch 50 to the steady position. This bypasses the timer 402 andcauses the solenoid 408 to be controlled directly by the footpedal 52 inFIG. 3. As long as the footpedal 52 is depressed, the solenoid 408remains energized to a state where pressurized air from channel 415 iscoupled to output channel 410. This provides a steady stream of viscousfluid for injection. When the footpedal is released, vacuum isautomatically coupled to the output channel 410 as in the case of the"one-shot" mode.

Referring to FIG. 9, there is shown a schematic diagram of the internalelectrical structure of the EFD Model 1000×L glue injector system unit32. Input power at 115VAC is applied to input port 470. Fuse F, andon/off switch 48 apply this power to a step down transformer 472 whichsteps the voltage down to 24 volts. Power on indicator lamp 474indicates when power is applied to the unit. Footpedal switch 52 isdirectly coupled to timer 402 as is steady switch 50, time control 54and solenoid 408. LED 406 lights when solenoid 408 is energized andpressurized air is being applied to the syringe. Lamp 480 lightswhenever the steady switch 50 is in a position to place the system unitin steady mode.

Although the invention has been described in terms of the preferred andalternate embodiments disclosed herein, those skilled in the art willappreciate many modifications which may be made without departing fromthe spirit and scope of the invention. All such modifications areintended to be included within the scope of the claims appended hereto.

What is claimed is:
 1. A method of injecting viscous material into aneye between a membrane and a retina using a pneumatic injection unithaving a pneumatic output and a pressure control for setting the maximumpneumatic pressure at said pneumatic output comprising the stepsof:pneumatically coupling a sterile syringe to said pneumatic output,said syringe having a hollow needle and a sharp point and storing asterile viscous material to be injected; applying pneumatic pressure tosaid syringe and examining the flow rate of said viscous materialemerging from said hollow needle; adjusting the pneumatic pressure untilthe flow rate is acceptable; placing the tip of said needle at theposition in the eye where the viscous material is to be injected;applying selected pneumatic pressure until a desired amount of saidviscous material has been injected; and automatically applying thevacuum to said pneumatic output upon termination of the application ofpneumatic pressure to said pneumatic output.
 2. A method of injectingviscous material into an eye between a membrane and a retina using apneumatic unit having pneumatic pressure generation apparatus includinga variable pressure control, and a pressure control switch and having apneumatic output coupled to a syringe having a needle with a sharppoint, said syringe storing the material to be injected comprising thesteps of:(1) setting the desired pneumatic pressure by observing theflow rate of material from the tip of said syringe during a sampleinjection outside said eye by activating said pressure control switch toapply pneumatic pressure to said output and by manipulating saidvariable pressure control until the desired flow rate has been achieved;(2) setting the desired time interval for a pneumatic pulse at saidoutput generated during a one-shot mode by selecting said one-shot modeby manipulation of a mode select switch and doing a sample injectionoutside the eye by activating said pressure control switch a pluralityof times to generate a plurality of pneumatic pulses at said output andmanipulating a variable timer control to adjust the time duration ofeach pulse until the desired time duration is found; (3) selectingeither said one-shot mode or a continuous mode by manipulation of saidmode select switch; (4) if the one-shot mode is selected, placing theneedle in the location in the eye where injection is desired andactivating said pressure control switch and holding said needle in thedesired place until the time duration of the pneumatic pulse haselapsed; (5) if the continuous mode is selected, placing the needle ofsaid syringe in any place in the eye where injection of said material isto occur and activating said pressure control switch until a desiredamount of material has been injected and then deactivating said pressurecontrol switch; (6) automatically applying a vacuum to said pneumaticoutput upon termination of the application of pneumatic pressurethereto; and (7) repeating steps 4, 5 and 6 at any other locations inthe eye deemed necessary.
 3. The method of claim 2 wherein saidpneumatic pressure generation apparatus includes vacuum generationapparatus and a variable vacuum control which applies a selected amountof vacuum to said syringe following the application of pneumaticpressure thereto, wherein the steps of performing sample injectionsoutside the eye include the substeps of manipulating said variablevacuum control until the level of vacuum applied following an injectionis sufficient to prevent excessive, undesired injection.
 4. A method ofinjecting viscous material into an eye between a membrane and a retinausing a pneumatic unit having pneumatic pressure generation apparatusincluding a variable pressure control, and a pressure control switch andhaving a pneumatic output coupled to a syringe having a needle with asharp point, said syringe storing the material to be injected comprisingthe steps of:(1) setting the desired pneumatic pressure by observing theflow rate of material from the tip of said syringe during a sampleinjection outside said eye by activating said pressure control switch toapply pneumatic pressure to said output and by manipulating saidvariable pressure control until the desired flow rate has been achieved;(2) setting the desired time interval for a pneumatic pulse at saidoutput generated during a one-shot mode by selecting said one-shot modeby manipulation of a mode select switch and doing a sample injectionoutside the eye by activating said pressure control switch a pluralityof times to generate a plurality of pneumatic pulses at said output andmanipulating a variable timer control to adjust the time duration ofeach pulse until the desired time duration is found; (3) selectingeither said one-shot mode or a continuous mode by manipulation of saidmode select switch; (4) if the one-shot mode is selected, placing theneedle in the location in the eye where injection is desired andactivating said pressure control switch and holding said needle in thedesired place until the time duration of the pneumatic pulse haselapsed; (5) if the continuous mode is selected, placing the needle ofsaid syringe in any place in the eye where injection of said material isto occur and activating said pressure control switch until a desiredamount of material has been injected and then deactivating said pressurecontrol switch; (6) automatically applying a vacuum to said pneumaticoutput upon termination of the application of pneumatic pressurethereto; (7) repeating steps 4, 5 and 6 at any other locations in theeye deemed necessary; and (8) injecting at a sufficient number of placesto separate said membrane from said retina and isolate or break allattachment points between said membrane and said retina followed byworking a horizontally oriented intraocular scissors through saidviscous material to the point of each attachment not yet broken andsevering the attachment followed by aspiration of the membrane and theremaining viscous material from the eye; wherein said pneumatic pressuregeneration apparatus includes vacuum generation apparatus and a variablevacuum control which applies a selected amount of vacuum to said syringefollowing the application of pneumatic pressure thereto; and wherein thesteps of performing sample injections outside the eye include thesubsteps of manipulating said variable vacuum control until the level ofvacuum applied following an injection is sufficient to preventexcessive, undesired injection.
 5. A method of injecting viscousmaterial into an eye between a membrane and a retina using a pneumaticunit having a variable pressure control, a variable timer control and apressure control switch and having a pneumatic output coupled to asyringe having a needle with a sharp point, said syringe storing thematerial to be injected comprising the steps of:setting the desiredpressure by observing the flow rate of material from the tip of theneedle of said syringe during a sample injection outside said eye byactivating said pressure control switch to apply pneumatic pressure tosaid output and by manipulating said variable pressure control until thedesired flow rate from the tip of said needle has been achieved; settingthe desired time interval for a pneumatic pulse at said output generatedupon activation of said pressure control switch and doing a sampleinjection outside the eye by activating said pressure control switch aplurality of times to generate a plurality of pneumatic pulses at saidoutput and manipulating said variable timer control to adjust the timeduration of each pulse until the desired time duration is found; placingthe tip of the needle at the location in the eye where the injection isto be made and activating said pressure control switch such that a pulseof pneumatic pressure having selected, programmable characteristics isapplied to said syringe thereby forcing a predetermined amount of saidmaterial from the tip of said needle; and repeating the step next aboveat a plurality of other locations if necessary.
 6. A method of injectingviscous material into an eye between a membrane and a retina using apneumatic unit having a variable pressure control, a variable timercontrol and a pressure control switch and having a pneumatic outputcoupled to a syringe having a needle with a sharp point, said syringestoring the material to be injected comprising the steps of:setting thedesired pressure by observing the flow rate of material from the tip ofthe needle of said syringe during a sample injection outside said eye byactivating said pressure control switch to apply pneumatic pressure tosaid output and by manipulating said variable pressure control until thedesired flow rate from the tip of said needle has been achieved; settingthe desired time interval for a pneumatic pulse at said output generatedupon activation of said pressure control switch and doing a sampleinjection outside the eye by activating said pressure control switch aplurality of times to generate a plurality of pneumatic pulses at saidoutput and manipulating said variable timer control to adjust the timeduration of each pulse until the desired time duration is found; placingthe tip of the needle at the location in the eye where the injection isto be made and activating said pressure control switch such that a pulseof pneumatic pressure having selected, programmable characteristics isapplied to said syringe thereby forcing a predetermined amount of saidmaterial from the tip of said needle; repeating the step next above at aplurality of other locations if necessary; and injecting at a sufficientnumber of places to separate said membrane from said retina and isolateor break all attachment points between said membrane and said retinafollowed by working a horizontally oriented intraocular scissors throughsaid viscous material to the point of each attachment not yet broken andsevering the attachment followed by aspiration of the membrane and theremaining viscous material from the eye.
 7. A method of injectingviscous material into an eye between a membrane and a retina using apneumatic unit having a variable pressure control, a variable timercontrol, and a pressure control switch and having a pneumatic outputcoupled to a syringe having a needle with a sharp point, said syringestoring the material to be injected, comprising the steps of:setting thedesired pneumatic pressure by observing the flow rate of material fromthe tip of the syringe during a sample injection outside said eye byactivating said pressure control switch to apply pneumatic pressure tosaid output and by manipulating said variable pressure control until thedesired flow rate has been achieved; setting a desired time interval fora pneumatic pulse at said output by performing a sample injectionoutside the eye by activating said pressure control switch a pluralityof times to generate a plurality of pneumatic pulses at said output andmanipulating said variable timer control to adjust the time duration ofeach pneumatic pulse until the desired time interval is found; placingthe tip of the needle at the location in the eye where the injection isto be made and activating said pressure control switch to inject aportion of said viscous fluid at the desired location; applying a vacuumto said output automatically upon termination of said pneumatic pulse;and repeating the injecting and vacuum application steps at any otherdesired location in the eye.